Elevated blood pressure in first trimester increases risk for blood pressure disorder later in pregnancy

Elevated blood pressure in the first trimester of pregnancy, or an increase in blood pressure between the first and second trimesters, raises the chances of a high blood pressure disorder of pregnancy, according to a study funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), part of the National Institutes of Health.

The study was led by Alisse Hauspurg, M.D., of the University of Pittsburgh School of Medicine and appears in the American Journal of Obstetrics and Gynecology.

The researchers sought to determine how revisions in guidelines for blood pressure in non-pregnant adults might apply to pregnant women. The results suggest that blood pressure readings lower than those traditionally used to identify women as having high blood pressure may indicate a higher risk for a hypertensive disorder of pregnancy, such as gestational high blood pressure, which develops after the 20th week of pregnancy, and preeclampsia, or high blood pressure and protein in the urine. Both conditions increase the risk for stroke in the mother and for stillbirth, preterm birth and low birth weight. Preeclampsia also increases the risk for eclampsia—life-threatening seizures for the mother.

The researchers analyzed data from Monitoring Mothers-to-Be (nuMoM2b), a study which sought to identify risks for birth and pregnancy complications in first-time mothers. For roughly 8,900 women, researchers compared blood pressure readings in the first and second trimesters of pregnancy to blood pressure status in the remainder of pregnancy. None of the women had stage 2 high blood pressure (140/90 mmHg or higher) at the time they entered the study.

Of women who had elevated blood pressure in the first trimester (120/80 to 129/80 mmHg), 30.3% developed a hypertensive disorder of pregnancy, a 42% higher risk than for women with normal blood pressure (less than 120/80 mmHg). Of women with stage 1 high blood pressure (130/80 to 130/89 mmHg), 37.8% developed a hypertensive disorder of pregnancy, an 80% greater risk than women with normal blood pressure. Stage 1 high blood pressure was associated with more than 2.5 times the risk for preeclampsia.

An increase in blood pressure between the first and second trimester also increased the risk of a hypertensive disorder of pregnancy. For example, even among women with normal blood pressure in the first trimester, an increase in systolic pressure (the top number) was associated with a 41% higher risk of any hypertensive disorder of pregnancy, compared to women with a decrease in systolic pressure between the first and second trimester. An increase in diastolic pressure (the bottom number) was associated with a 23% higher risk of a hypertensive disorder, compared to women who had a decrease in diastolic pressure during this time.

About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): NICHD conducts and supports research in the United States and throughout the world on fetal, infant and child development; maternal, child and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit http://www.nichd.nih.gov.

About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.

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Reference

Hauspurg A, et al. Early pregnancy blood pressure category and trajectory and risk of hypertensive disorders of pregnancy. American Journal of Obstetrics and Gynecology. 2019